Measurement of human chorionic gonadotropin (HCG) concentrations in paired maternal and cord sera using an assay specific for the beta subunit of HCG.

Human chorionic gonadotropin (HCG) concentrations were determined in paired maternal and cord sera using an essay specific for the beta subunit of HCG. The sera of 46 mothers and 46 infants, 24 female and 22 male, were studied. Results were compared to those obtained using a radioimmunoassay for luteinizing-hormone (LH) which cross-reacted with HCG. With either assay system, mean maternal HCG concentrations were lower when the sex of the fetus was male than when the sex of the fetus was female. Mean cord HCG concentrations of male (0.09 +/- 0.02 IU/ml) and female (0.09 +/- 0.04 IU/ml) infants were not different as determined by the beta HCG assay. In contrast, the mean cord serum concentration of HCG was significantly greater (P less than .005) in male infants (0.29 +/- 0.05 IU/ml) than in female infants (0.23 +/- 0.09 IU/ml) as determined by the cross-reacting assay. HCG concentrations were lower in both maternal and cord sera when assayed in the specific HCG system than when assayed in the cross-reacting system. There was a significant correlation (r=.9; P less than .005) between the results obtained with the two assays in both maternal and cord blood. Regardless of the assay system employed, the cord serum concentration of HCG was markedly less than the corresponding maternal serum concentration. There was no correlation between maternal and cord serum HCG concentrations with either assay. These data are in agreement with the results of previous studies employing less specific methodology which indicated that maternal serum HCG concentrations were less when the fetus was male than when it was female. They are also consistent with a placental barrier effect with regard to HCG transfer to the fetus. The difference in results obtained in cord blood with the two assay systems suggests that the newborn male infant secretes more LH and/or alpha LH subunits than the newborn female infant.